This invention relates to the treatment of hydrocarbon oils and, more particularly, to the hydrocracking of heavy hydrocarbon oils in the presence of iron and petroleum coke additives.
Hydrocracking processes for the conversion of heavy hydrocarbon oils to light and intermediate naphthas of good quality for reforming feedstocks, fuel oil and gas oil are well known. These heavy hydrocarbon oils can be such materials as petroleum crude oil, atmospheric tar bottoms products, vacuum tar bottoms products, heavy cycle oils, shale oils, coal derived liquids, crude oil residuum, topped crude oils and the heavy bituminous oils extracted from oil sands. Of particular interest are the oils extracted from oil sands and which contain wide boiling range materials from naphthas through kerosene, gas oil, pitch, etc. and which contain a large portion of material boiling above 524.degree. C., equivalent atmospheric boiling point.
As the reserves of conventional crude oils decline, these heavy oils must be upgraded to meet the demands. In this upgrading, the heavier material is converted to lighter fractions and most of the sulphur, nitrogen and metals must be removed.
This can be done either by a coking process, such as delayed or fluidized coking, or by a hydrogen addition process such as thermal or catalytic hydrocracking. The distillate yield from the coking process is about 70 wt. % and this process also yields about 23 wt. % coke as byproduct which cannot be used as fuel because of low hydrogen:carbon ratio, and high mineral and sulphur content. This coke derived from heavy oil coking operations is referred to hereinafter as "petroleum coke".
Work has also been done on an alternate processing route involving hydrogen addition at high pressures and temperatures and this has been found to be quite promising. In this process, hydrogen and heavy oil are pumped upwardly through an empty tubular reactor in the absence of any catalyst. It has been found that the high molecular weight compounds hydrogenate and/or hydrocrack into lower boiling ranges. Simultaneous desulphurization, demetallization and denitrogenation reaction take place. Reaction pressures up to 24 MPa and temperatures up to 490.degree. C. have been employed.
In thermal hydrocracking, the major problem is coke or solid deposition in the reactor especially when operating at relatively low pressures, and this can result in costly shut-downs. Higher pressures reduce reactor fouling. At 24 MPa and 470.degree. C., the coke deposition can be substantially eliminated. However, plant operations at high pressures involve higher capital and operating costs.
It has been well established that mineral matter present in the feedstock plays an important role in coke deposition. Chervenak et al, U.S. Pat. No. 3,775,296 shows that feedstock containing high mineral content (3.8 wt.%) has less tendency to form coke in the reactor than feed containing low mineral matter (&lt;1 wt. %). Other studies have shown that a high mineral content had no apparent effect on pitch conversion and desulphurization, but suppress coke deposition in the reactor and general reactor fouling.
The addition of coke carriers was proposed in Schuman et al., U.S. Pat. No. 3,151,057, who suggested the use of "getters" such as sand, quartz, alumina, magnesia, zircon, beryl or bauxite. These "getters" could be regenerated after use by heating the fouled carrier with oxygen and steam at about 1090.degree. C. to yield regeneration-product-gases containing a substantial amount of hydrogen. It has been shown in Ternan et al, Canadian Patent 1,073,389 issued Mar. 10, 1980 and Ranganathan et al, U.S. Pat. No. 4,214,977 issued July 29, 1980, that the addition of coal or coal-based catalyst results in a reduction of coke deposition during hydrocracking. The coal additives act as sites for the deposition of coke precursors and thus provide a mechanism for their removal from the system.
The use of these coal based catalysts allows operation at lower pressures and at higher conversions. The use of coal and Co, Mo and Al on coal catalyst is described in Canadian Patent 1,073,389, the use of iron-coal catalysts in U.S. Pat. No. 4,214,977, and the use of fly ash in Canadian Patent 1,124,194.
In U.S. Pat. No. 3,775,286, a process is described for hydrogenating coal in which the coal was either impregnated with hydrated iron oxide or dry hydrated iron oxide powder was physically mixed with powdered coal. Canadian Patent 1,2020,588 describes a process for hydrocracking heavy oils in the presence of an additive in the form of a dry mixture of coal and an iron salt, such as iron sulphate.
It is the object of the present invention to utilize the petroleum coke, which is formed in coking processes such as delaying coking or fluidized coking, to formulate an iron based additive to be used in hydroconversion of heavy oils to lighter products.